Germination Inhibition of Alfalfa by Two‐Component Salt Mixtures

Soil and water salinity can severely constrain agricultural production by reducing plant stands and growth. Breeders have used germination in saline (NaCI) media to screen plant germplasm for salt tolerance. However, salt tolerance during germination in NaCI may not adequately describe the ability of seeds to germinate in mixtures of salts. Naturally occurring combinations of salts may be more or less inhibitory than the individual salts alone. The objective of this research was to quantify the effects of individual as well as two‐component mixtures of various salts and ions on the seed germination of alfalfa ( Medicago saliva L.). Seeds of the alfalfa cultivars Condor and Rambler were germinated in petri plates in a darkened growth chamber maintained at 25 °C and exposed to biologically equivalent concentrations of one‐ and two‐salt solutions of NaCI, Na 2 SO 4 , KCI, K 2 SO 4 , MgCl 2 , and MgSO 4 . Specific interaction effects of the salts in two‐salt combinations were detected; however, as indicated by simple correlations, germination was affected more by concentration of Na+ than any other single variable. When all independent variables were considered, concentrations of Cl − and Mg 2+ were more important than Na + and the other ions, choice of cultivar, or the osmotic tension and pH of the solutions. While maximum genetic gain in salt tolerance during germination of alfalfa seeds may only be achieved by selection in solutions containing more than one salt, selection in NaCI solutions may account for most of the potential gain.